Electric control system



Sept. 29, 1942. l. M LNAR 2,296,941

ELECTRIQCONTROL SYSTEM Filed Sept. 16, 1939 9 Sheets-Sheet 2 Q 0 ll ATTORN EYS WM 289 AP -fl Indicczzor Panel Sept. 29, 1942'.-

l. MOLNAR ELECTR IC CONTROL SYSTEM Filed Sept. 16, 1959 9 Sheets-Sheet 8 ATTORN EYS.

Patented Sept. 29, 1942 ELECTRIC CONTROL SYSTEM Imre Molnar, Chicago, Ill., assignor to Associated Electric Laboratories, Inc., Chicago, 111., a corporation of Delaware Application September 16, 1939, Serial No. 295,345

17 Claims.

The present invention relates to electric control systems and more particularly to automatic switching apparatus therefor.

Electric control systems frequently comprise a plurality of trunks each including a number of control circuits, a plurality of automatic switches each operative to seize any one of the trunks, and means for selectively governing the control circuits in a seized one of the trunks. It often occurs that the devices controlled by the control circuits in the various trunks are so interrelated that the control of one of the devices by way of one of the control circuits in one of the trunks is inconsistent and conflicting with the control of another of the devices by way of another of the control circuits in another of the trunks. For example, in an airport lighting and trafiic control system comprising a flying field having a plurality of airplane runways thereon, wherein some of the runways are arranged in intersecting relationship with respect to other of the runways and in non-intersecting relationship with respect to still other of the runways it is inconsistent and conflicting to govern the control circuits in a trunk extending to the illumination means and the trafiic signals individually associated with one of the runways while the control circuits in a trunk extending to the illumination means and the trafiic signals associated with an intersecting runway are being governed.

Accordingly, it is an object of the present invention to provide in an electric control system of the type noted including a plurality of trunks, a plurality of automatic switches each having access to the trunks and embodying an improved arrangement for testing both a selecting marking and ai seizure marking of any one of the trunks prior to actual seizure thereof, wherein a trunk is marked against selection when it has been previously selected by another of the automatic switches and marked against seizure when a conflicting trunk has been previously selected by another of the automatic switches.

Another object of the invention is to provide in an electric control system of the type noted including a plurality of trunks, wherein some of the trunks have one digit designations and other of the trunks have two digit designations, improved switching apparatus of the numerical type, which is so connected and arranged that it is responsive to the digits 1 or 2 respectively to select the trunks having the corresponding designations I or 2 and responsive to the digit 1 followed by the digits 1 or 2 respectively to select the trunks having the corresponding designation H or l2.

A further object of the invention is to provide an electric control system comprising improved switching apparatus which is simple and economical to manufacture and which is thoroughly reliable in operation.

The features of the present invention are illustrated as being incorporated in an airport comprising a flying field having a plurality of airthereof; and the group of trafiic signals associated with each runway comprises two targets and two arrows, the targets being associated with the opposite ends of the runway and the arrows being associated with the stretch of the runway.

\ Two trunks are individually associated with each runway, the two trunks individually associated with a runway being individually selected in accordance with the direction of airplane traific on the runway. Also, each trunk includes a plurality of control circuits for selectively governing the illumination means and the traffic signals associated with the associated runway. Further, the airport comprises a dispatcher station including apparatus for selectively controlling the illu- -mination means and the traffic signals and for supervising the control thereof.

In accordance with one feature of the invention the system comprises an impulse receiver unit, a plurality of numerical selector links each having access to the trunks, and a plurality of control devices. at the dispatcher station individually associated with the selector links, each of the control devices having a normal position and two operated positions. Also, the system comprises means controlled by the operation of any one of the control devices from its normal position to one of its operated positions for selecting the corresponding one of the selector links for use and for associating the selected selector link with the impulse receiver unit and means controlled when the selected selector link is asso-- The impulse receiver unit is operative in response a to any numerical signal to test the selection marking of a corresponding one of the trunks, and a signal transmitter is provided at the dispatcher station which is operative to transmit different numerical signals to the impulse receiver unit. Jfhe impulse receiver unit comprises means controlled in the event the one trunk is tested as not marked against selection for preparing the selected selector link to select the one trunk, for causing the selected selector link to mark the one trunk against selection by the other of the selector links, and for marking certain other of the trunks against seizure by the other selector links.

lhe selected selector link comprises means controlled by the operation of the one control device from its one operated position back to its normal position for causing the selected selector link to select the one trunk and to test the seizure marking thereof, means for causing the selected selector' link to seize the one trunk in the event it is tested as not marked against seizure, and means controlled by the operation of the one device from its normal position to the other of its operated positions for releasing the selected selector link. When the selected selector link is released the one trunk is marked to be selected by the other of the selector links and the other trunks are vmarked to be seized by the other of the selector links. Finally, a device is provided at the dispatcher station for selectively governing the control-circuits in a seizedone f the trunks.

in accordance with another feature of the inventionisome of the trunks have one digit designations and other of the trunks have two digit designations and the impulse receiver unit is so connected and arranged that it is responsive to thedigits l or'2 respectively to mark for selection the'trunks designated I ,or 2 and responsive to'the digit '1 followed by the digits 1 or 2 respectively to mark for selection the trunks designated I I or I2. .Further, the impulse receiver unit causes the selected selector link to seize the particular trunk marked for selection in the event it is. not :marked against seizure.

. Further features of the invention pertain to the particular connection and arrangement of the circuit. elements of the system, whereby the above-:outlined and additional operating features are attained.

. The novelfeatures believed to be characteristic of .the invention are set forth with particularity in the appended claims. The invention both as to :its organization and method of operation, together with further objects and advantages thereof, will best be understood by reference to the following. specification taken in connection with the accompanying drawings, in which Figure 1 illustrates diagrammatically an airport lighting and traffic control system; Fig. 2 illustrates diagrammatically an indicator panel incorporatedin the system; 'Fig. 3 illustrates diagrammatically a control panel incorporated in the system; andFigs. 4 to 9, inclusive, taken together, illustrate diagrammatically the details of the control .apparatus incorporated in the system, this apparatus including an impulse receiver unit, anumber of numerical selector links, and control means therefor embodying the present invention.

Referring now more particularly to the drawings, the airport there illustrated comprises a flying field sec and a dispatcher control tower or station 'IIiI,,from which the entire flying field'i's clearly visible to. the dispatcher. The fly- 75 ing field IElfl comprises nine paved runways over which airplane traffic may be routed in either direction, whereby the runways comprise eighteen directional runway ends Ri to R58, inclusive, for airplane traffic. Some of the runways are arranged in parallel relationship, while others of the runways are arranged in intersecting relationship, thus providing a general crisscross pattern upon the flying field. Further, the flying field is provided with a paved rectangular boundary way communicating with each of the runway ends in order to facilitate movement of the airplanes from the hangers to the various runway ends.

The general boundary of the flying field its is outlined by a number of boundary lamps indicated at I93; while all elevated structures disposed'adjacent the boundary of the flying field are provided with hazard lamps indicated at I85. Also flood lamps indicated at III, H2, H3 and 1! Id are disposed substantially at the corners of the boundary of the flying field for general illumination purposes. Further, a revolving'beacon indicated at IIJI is associated with the flying field .IiZ'U for the purposeof marking the location of the airport to airplanes aloft; and rotatable T lamps indicated at H5 are disposed upon the flying field for the purpose of signaling wind direction to airplanes aloft. Finally, a number of gates are disposed along the boundary of the flying field to facilitate loading of the airplanes, each of the gates being provided with lamps for illumination purposes. For example, the first gate is provided with gate lamps indicated at H6. 'Finally, the margins of each runway are provided with rows of flush-type contact lamps in order to mark the boundaries thereof. For example, the margins of the runway R 3R2;i are provided with rows of contact lamps indicated at I20.

In order to control airplane trailic upon the runways, each runway end is provided with an arrow and a target, the arrow being of the flush type, visible to an airplane aloft, and the target being-of the elevated type, visible only to an airplane on the flying field. For example, the runway ends RI, R4, RI2 and RIB are provided respectively with arrowslAR'l ARA, ARI2 and ARI 5 and targets TR'I, "3R4, TRI2 and TRI5. Preferably, each of the arrows is substantially identical to the arrow A1315, which comprises a red lamp I2I and agreen lamp I22 disposed therein; while each of the targets is substantally identical to the'target TREE, which comprises a red lamp I23, anamber lamp I24 anda green lamp disposed therein.

:Inorder to control the illumination of the common apparatus comprising the revolving beacon IIL'the flood lamps III, 2,153 and H4, the T lamps N5, the boundary lamps I83 the hazard lamps :IM, and the gate lamps and selectively to control the various arrows and targets individually associated with the runway ends, control apparatus I82 is'provided in the dispatcher control tower Ifil. Also, there are provided in the dispatcher control tower Iii-I a control panel 336 andan-indicator panel 230, the control panel 39% being arranged to govern the control apparatus I02 and the indicator panel 208 being arranged to indicate illumination of the runways and the settings of the various arrows and targets associated with the runway ends. Preferably, the control panel 390 isdisposed in a substantially horizontal position on the top of the desk of the-dispatcher, whiie-theindicator panel 2% is disposed in either an inclined or a vertical position in front of the deskrof the dispatcher, so that the dispatcher may readily operate the apparatus onthe control panel 300 and observe upon the indicator panel 290 the illumination of the runways and the settings of the arrows and targets associated with the runway ends on the flying field I00.

Referring now to Fig. 2, the illustrated indicator panel 200 comprises an opaque sheet which is cut out and covered with translucent material in order to provide a general crisscross pattern corresponding precisely to the crisscross pattern of the runways on the flying field I60. Also, the ends of the various strips of translucent material carry a number of characters RI to Rt 8, inclusive, identifying the corresponding runway ends on the flying field, a number of arrows ARI to ARIB, inclusive, identifying the corresponding arrows associated with the runway ends on the flying field, and a number of targets TRI and TRIS, inclusive, identifying the corresponding targets associated with the runway ends on the flying field. A series of lamps are disposed below each of the translucent strips on the indicator panel which are adapted to be illuminated in accordance with the illumination of the contact lamps disposed along the margins of the corresponding runway on the flying field. For example, the series of lamps 2'56 are disposed below the strip of translucent material on the indicator panel corresponding to the runway R5RI5. Red and green lamps are disposed below each of the arrows carried by the translucent strips on the indicator panel which are adapted to be illuminated in accordance with the illumination of the red and green lamps in the arrows associated with the corresponding runway ends on the flying field. For example, the arrow ARI5 carried by the end RI5 of the translucent strip on the indicator panel has disposed therebelow a red lamp 2' and a green lamp 212. Red, amber and green lamps are disposed below each of the targets carried by the translucent strips on the indicator panel which are adapted to be illuminated in accordance with the illumination of the red, amber and green lamps in the targets associated with the corresponding runway ends on the flying field. For example, the target TRI5 carried by the end RI5 of the translucent strip on the indicator panel has disposed therebelow a red lamp 213, an amber lamp 274 and a green lamp 215.

Further, the indicator panel 280 comprises three groups of pilot lamps individually corresponding to three selector links included in the control apparatus I82. Each group of pilot lamps comprises eighteen pilot lamps individually corresponding to the eighteen runway ends on the flying field. For example, the first group of pilot lamps individually associated with the first selector link'in the control apparatus Hi2 comprises the pilot lamps 2M to 2I8, inclusive, which respectively correspond to the runway ends RI to RI8, inclusive. Similarly, the first pilot lamp 22I in the second group of pilot lamps individually associated with the second selector link in the control apparatus I02 is individually associated with the first runway end RI; while the first pilot lamp 2M in the third group of pilot lamps individually associated with the third selector link in the control apparatus IE2 is individually associated with the runway end RI. It is noted that when one of the selector links in the control apparatus IE2 is operated to select one of the runway ends on the flying field, the pilot lamp corresponding to the selected runway end in the group of pilot lamps corresponding to the selected link utilized is illuminated. Accordingly, the illumination of the pilot lamps in the three groups of pilot lamps indicates to the dispatcher the particular runway end which has been selected by a particular selector link in the control apparatus I02.

Referring to Fig. 3, the control panel 300 comprises three groups of keys individually corresponding to the three selector links in the control apparatus I62. For example, the first group of keys comprises the illustrated keys IKI, IK2 and IK3; the second group of keys comprises the illustrated keys ZKI, 2K2 and 2K3; while the third group of keys comprises the illustrated ke'ys 3KI, 3K2 and 3K3. Preferably, the three keys in each of the three groups of keys are connected and arranged to perform similar functions in the respective selector links in the control apparatus I 62. For example, the key IKI comprises a select-release key for the first selector link; the key IK2 comprises a take off-landemergency stop key for the first selector link; while ,the key IK3 comprises a traflic on-ofi-runway and trafic on key for the first selector link.

Also, the control panel 396 comprises a group of common keys, including the keys KI to KIO, inclusive, the keys KI to Kt, inclusive, being arranged to control the illumination of the. gate lamps associated with the gates I to 6, respectively; the key KI being arranged to control the illumination of the boundary and hazard lamps; the key K8 being arranged to controlthe illumination of the T lamps; and the key K9 being arranged to control the illumination of the revolving beacon. Finally, the key KI!) is arranged to control the intensity of illumination of the contact lamps disposed along the margins of the various runways on the flying field. More particularly, by manipulating the key Kli! the illumination of the contact lamps disposed along themargins of the various runways on the flying field may be varied to three different intensities; namely, normal, dim and bright. Further, a group of pilot lamps 3H to M9, inclusive, is provided on the control panel 380 and individually associated with the keys KI to KS, respectively, these pilot lamps being so connected and arranged that they are illuminated in accordance with the operation of the respective keys. Also, four keys KII, Kl2, KI3 and KM are provided on the control panel for the purpose of controlling the illumination of the respective flood lamps III, H2, H3 and H4. Further, there is provided on the control panel a push button pattern 34!] which corresponds precisely to the general criss-cross pattern of the runways on the flying field. Also, the push button pattern 340 comprises eighteen push buttons FBI to PRIS, inclusive, respectively positioned on the pattern 340 in accordance with the positions of the various runway ends on the flying field. More particularly, each of the push buttons is connected and arranged in such a manner that it is operative, when depressed, to cause the amber lamp in the target associated with the corresponding runway end on the flying field to flash and to cause the amber lamp in the target associated with the corresponding end of the translucent strip on the indicator panel to flash. For example, when the push button PRI5 is depressed, the amber lamp I24 in the target TRIS associated with the corresponding runway end RI5 on the flying field is flashed and the amber lamp 274 in the target TRI5 associated with the corresponding end RI of the translucent strip on the indicator panel is flashed.

Finally, the control panel 350 is provided with a number dial I comprising a rotatablefinger disk 352 and a finger stop 303, this number dial being of the usual'automatic telephone type. The number dial I is so connected and arranged that it is operative to control a selected one of the selector links in the control apparatus I02 in order to cause the selected selector link to select any desired one of the runways on the flying field for the purpose of governing the illumination of the contact lamps disposed along the margins of the selected runway and the settings of the signals individually associated with the opposite ends thereof.

Referring now to Figs. 4 to 9, inclusive, the control apparatus I02 comprises certain common equipment associated with the common keys KI to KID, inclusive, on the control panel 300 and with the three'selector links, an impulse receiver unit I05 commonly associated with the three groups of keys on the control panel. and three selector links commonly associated. with the impulse receiver unit, the first selector link being indicated at 695.

This common equipment comprises a stepdown transformer 445, having a primary winding 446 connected by way of a control switch S408 to a source of low voltage A. C. supply 401, and a secondary winding 447 included in the various control circuits governed by the keys on the control panel 300. Also, this common equipment includes a power transformer 6I0 having a pri-' mary winding arranged in three sections GII, 6I2 and 5I3, and a secondary winding 654, and two choke coils 6I5 and GIG. The various series of contact lamps I20, 635, 635, etc., disposed along the margins of the runways on the flying field, are adapted to be respectively connected across the secondary winding 6M of the power transformer 6I0 by, a number of slave relays R620, R522, R624, etc.; while the various sections of the primary winding of the power transformer BIH are adapted to be connected in a predetermined manner to a source of high voltage A. C. supply 50I by a control switch S502 and three two-position switches 85h], S520 and S530. Each of the two-position switches S5I0, S520 and- S530 is of the heavy duty, double acting, solenoid type, comprising operating and releasing windings. A circuit networkis provided for controlling the operating and releasing windings of the two-position switches S5I0, S520 and S530, which comprises three switch control relaysR llfl, R-4I-5 and R520, three lockout relays R425, R430 and R435, and a control relay R450.

Further, the common equipment comprises a group of six gate relays, including the gate relay R550; a group of six gate slave relays, including the gate slave relay R560; a group of eighteen target relays, including the target relay R545; and a group of eighteen target slave relays, including the target slave relay R565. It is noted that the gate relays are individual to the re spective gates associated with the flying field, the gate relay R550 being individual to the first gate and being operative to complete a circuit for energizing the gate lamps II6 associated with the first gate; while the target relays are individual to the respective targets associated with the runway ends on the flying field, the target relay R540 being individual to the target TR5 associated with the runway end R5 on the. flying field and being operative to complete'a circuit for illuminating the amber lamp I30 in the target TR5. Each of the circuits for illuminating the amber lamps in the various targets includes .a flasher in order to cause the amber lamp to flash, the circuit for illuminating the amber lamp I30 in the target TR5 including the flasher 553. Also, this common equipment includes a boundary and hazard relay R545 and an associated boundary and hazard slave relay R555, the boundary and hazard relay R545 being operative to complete the circuits for illuminating the boundary and hazard lamps I03 and I04.

It is noted that the gate slave relays are arranged to control the illumination of the group of pilot lamps disposed on the control .panel 300, the gate slave relay R500 being arranged to control the illumination of the first pilot lamp 3 in this group of pilot lamps. The boundary and hazard slave relay R555 is arranged to control the illumination of the pilot lamp 3I'I in the group of pilot lamps on the control panel 300; while the target slave relays are arranged to control the illumination of the amber lamps in the'various targets associated with the miniature runways on the indicator panel 200, the

relay R950 individually associated with the runway end RIZ; a group of eighteen land relays accessible to each of the selector links and individually corresponding to the eighteen runway ends on the flying field, this group including the land relay R905 individually associated with the runway end RI2; a group of eighteen emergency stop relays accessible to each of the selector links and individually corresponding to the eighteen runway ends on the flying field, this group including the emergency stop relay RQIO individually associated with the runway end RI2; and a group of nine contact lamp relays accessible to each of the selector links and individually corresponding to the nine runways on the flying field, this group including the contact lamp relay'R9I5 individual to the runway R4RI2.

It is noted that the various take off, land and emergency stop relays control the illumination of the red and green lamps in the targets and arrows associated with the various runway ends on the flying field; while the various contact lamp relays control the illumination of the various-series of contact lamps disposed along the margins of the various runways on the flying field. For example, the take off relay R900 is arranged to control the illumination of the red lamp I44 in the arrow ARIZ associated with the runway end RI2, the illumination of the green lamp I41 in the target TR l associated with the runway end R4, and the illumination of the green lamp I42 in the target 'IRI2 associated with the runway end RIZ; the land relay R905 is arranged to control the illumination of the red lamp I40 in the target TRIZ and the illumination. of the green lamp I 43 in the arrow ARIZ; the emergency stop relay RSIB is, arranged to control the illumination of the red lamp I44 in the arrow ARI2, the red lamp I40 in the target TRIZ, and the red lamp I45 in the target TR4; and the contact lamp relay R9-I5 is arranged to control the energization of the slave relay R520, thereby to control the illumination of the series of contact lamps I20 disposed along the margins of the runways R4-R|2 on the flying field.

Also, the common equipment comprises a group of eighteen slave relays, including the slave relays R930 and R950, for controlling the illumination of the red lamps in the various targets associated with the miniature runway ends on the indicator panel, the slave relays R930 and R950 being arranged to control the illumination of the red lamps 283 and 290, respectively, in the targets TRIZ and TR I; a group of eighteen slave relays, including the slave relays R925 and R945, for controlling the illumination of the green lamps in the various targets associated with the miniature runway ends on the indicator panel, the slave relays R925 and R945 being arranged to control the green lamps 285 and 288, respectively, in the targets TRIZ and 'IR; a group of eighteen slave relays, including the slave relay R950, for controlling the illumination of the red lamps in the various arrows associated with the miniature runway ends on the indicator panel, the slave relay R940 being arranged to control the red lamp 282 in the arrow ARI2; a group of eighteen slave relays, including the slave relay R935, for controlling the illumination of the green lamps in the various arrows associated with the miniature runway ends on the indicator panel, the slave relay R935 being arranged to control the green lamp 28I in the arrow ARIZ; and a group of nine slave relays, including the slave relay R920, for controlling the illumination of the series of lamps disposed below the translucent strips on the indicator panel, the slave relay R928 being arranged to control the illumination of the series of lamps 215 disposed below the translucent strip R4-RI2 on the indicator panel.

The arrangement of the illumination means and the traffic signals with respect to the runways on the flying field, the arrangement of the supervisory apparatus in the dispatcher tower and the connection and arrangement of the control circuit network for the illumination means, the traflic signals and. the supervisory apparatus are disclosed and claimed in the copending application of Thomas A. Logan and Imre Molnar, Serial No; 295,344, filed September 16, 1939.

The impulse receiver unit 100 comprises a rotary switch S189, including three wipers 18I, 183 and 185 provided with individually associated contact banks 182, 184 and 188 and a magnet M135 for simultaneously driving the wipers noted into engagement with the contacts in the associated contact banks. Also, a set of switch springs S1I8 is operatively associated with the wipers noted of the rotary switch S180 and arranged to be operated into engagement when the wipers of the rotary switch are operated away from their normal positions. Further, the impulse receiver unit 180 comprises a start relay R140, a hold relay R159, a test relay R130, a switching relay R198, a slave relay R190 and a circuit network.

Preferably, each of the selector links is identical to the illustrated first selector link 805, which comprises a rotary switch S800. including five wipers SM, 803, 805, 801 and 809 provided with individually associated contact banks 882, 884, 808, 858 and 8I0 and a magnet M880 for driving the wipers noted into engagement with the contacts in the associated contact banks. Also, the selector link 895 comprises a rotary switch S820 including five wipers 82!, 823, 825,

821 and 829 provided with individually associated contact banks 822, 824, 826, 828 and 830 and a magnet M885 for driving the wipers noted into engagement with the contacts in the associated contact banks. Further, the selector link 895 comprises a test relay R850, a lookout relay R840, nine marking relays including the relay R890, which individually correspond to the nin runways, relay R880, a switch-through relay R810 and a circuit network. Also, it is noted that the wiper 809 and associated contact bank SW of the rotary switch S800 are connected and arranged to control the illumination of the pilot lamps in the first group of pilot lamps, including the pilot lamp 2 I2, on the indicator panel.

Before proceeding with a detailed description of the operation of the lighting and traflic control system, a brief explanation of the method of controlling the signals associated with the opposite ends of the various runways on the flying field in order to coordinate the movements of different airplanes is set forth below.

In order to control the take oif of an airplane from the flying field I00 the dispatcher in the dispatcher control tower IOI first determines in accordance with the direction of the prevailing windthe particular runway which is to be utilized by the airplane in taking off and the direction of take off on the runway and then views the flying field and the indicator panel 200 in order to satisfy himself that the flying field is clear as far as the determined runway is concerned. The dispatcher then selects the particular one of the three selector links which is to be utilized by operating the select key on the control panel 300 corresponding to the selected link. The dial 30I on the control panel is then operated to cause the selected link to select the determined runway. After the determined runway has been selected, the dispatcher operates the take off key of the selected link on the control panel, thereby to cause the signals associated with the opposite ends of the selected runway to be set in a predetermined manner. More particularly, the target associated with the near end of the selected runway displays a green light; the target associated with the remote end of the selected runway displays a green light; and the arrow associated with the near end of the selected runway displays a red light. The display of the green light by the near target indicates to the pilot in the airplane that he may safely taxi his airplane upon the near end of the selected runway; the display of the green light by the remote target indicates to the pilot in the airplane that his airplane may proceed along the selected runway and take off; while the display of the red light by the near arrow indicates to a pilot in an airplane aloft that the selected runway is in use A and that he may not safely land his airplane thereupon.

In order to control the landing of an airplane upon the flying field I00 the dispatcher in the dispatcher control tower IOI proceeds to select one of the runways with a selected one of the links in the previously described manner, and then operates the land key of the selected link on the control panel, thereby to cause the signals associated with the opposite ends of the selected runway to be set in a different predetermined manner. More particularly, the target associated with the near end of the selected runwai displays a red light, the target associated with the remote end of the selected runway is dark,

and the arrow associatedwith. the near end. of the selected runway displays a green light... The display of the redlightby the near target indicates to a pilot in. an airplane on the flying field that the selected runway is in use and that he may not safely taxi his airplane upon: the near and of the, selected runway; and the darkened condition. of the remote target indicates; to a pilot; in an airplane on the flying field that the selected" runway is in use and that he may not safely take off thereon; while the display of the green light by' the near arrow indicates to the pilot in the airplane aloft that the selected runway' is in readiness for use to land his airplane thereupon.

Finally, it is noted that the dispatcher in the dispatcher controljtower- It], after selecting a runwayon the'flying field for the use of either an airplane which is to takeofi'thereupon or an airplane which is to land thereupon, may block the actual use of the selected runway by operating the emergency stop key'of the-selected link on the control panel, thereby to cause thesignals associated with the'opposite endsof the selected runway to be set in a further predetermined manner. More particularly, the near target displays a red light, the remote target displays a red light, and thenear arrow displays a red-light." The display of the red light by theneartarget indicates to a pilot in'an airplane on the flying field that he may not safely taxi his airplane upon the near end of. the selected runway; the display of the red light by the remote target indicates to a pilot in an airplane upon the near end of the selectedrunway that his airplane may i not: safely take off thereupon; while the display of the red light by the near arrow'indicates to a pilot in an airplane aloft that he may not safely utilize-the selected runwaytov land his airplane.

In order to conserve time in the handling of airplane traffic, the dispatchermay utilize the push button pattern 349 on thecontrol panel 360, thereby to cause the target'associated with any one of the runways to display a flashing amber light. This may be accomplished merely by depressing the particular push button on the push button pattern Slit-corresponding to the target associated withthe desiredrunway end on the flyingfield. This facility is utilized particularly in directing airplanes oiT of the flying field after they have landed on aselected one of. the runways. For example, assuming'that an airplane has landed; on therunway end RIZ, on the flying field and is taxiing toward the center intersection, the dispatcher in the dispatcher control tower: till may operate-the-push button PR on the push buttonpattern 3-40 corresponding tothe target TR5 associated with the runway end R5 on the flying field, thereby towcause the target TR5 to'displa-y a flashing amber light. The display of the flashing amber light by the target TRB indicates to the pilot in the airplane taxiing along the runway end R12 toward the center intersection that heis to turn into the runway end R5, upon reaching the center intersection, thereby to clear the runway end R12 for the use of other airplanes.

Further, it is noted that the control apparatus Hi2, the signals on the flying field Hill and the indicator panel 200' are so connected and arranged that, when the dispatcher controls at the control panel 300 the signals associated with the opposite ends of any one of the runways on the flying field to. display predetermined indications, the signals associated with the opp0- site ends of the corresponding runway on the miniature pattern of the flying field on the indicator panel 259 are controlled to display like indications. Accordingly, the signals displayed on the miniature pattern of the flying field on the indicator panel 2% always correspond to the actual signals displayed on the flying field.

Considering now the operation of the control apparatus l 62 by the dispatcher in the dispatcher control tower IEH, after the dispatcher has determined in accordance with the direction of th re- Vailing wind on the flying field a particular one of the runways on the flying field for use and the direction of airplane traffic thereon, he selects one of the selector links to be utilized to select the determined runway, as previously noted. Assuming that the dispatcher selects the first selector link 895 to be utilized to select the determined runway on the flying field, this is accomplished by operating the key IKI on the control panel 3% to its select position. When the key iKi is operated to its select position, a circuit is completed, at the contacts 1-24 thereof, for energizing in series the upper and lower windings of the lookout relay R3 30. This circuit extends from ground by way of the contacts 126 of the key IKI, U595, the upper winding of R840, the contacts ,852, the lower winding of R848 and the resistor 816 to battery. It is noted that the point between the terminal of the lower winding of the lookout relay R840 and the resistor 83B is multiplied to the other selector links. Accordingly, the upper and lower windings of the lockout relay R856 are suificiently energized to cause this relay to operate only in the event the keys corresponding to the key HQ in the other selector links occupy their normal positions. Assuming that the above-mentioned condition prevails in the second and third selector links, the upper and lower windings of the lookout relay R858 are sufliciently energized at this time in order to cause the lockout relay R845 to operate. Upon operating, the lockout relay R840 completes, at the contacts 84!, an obvious holding circuit for energizing the upper winding thereof and an obvious path for short-circuiting the lower winding thereof, thereby to retain the lookout relay Refill in its operated position and to load the resistor 8-76. When the resistor 315 is thus loaded by the lookout relay R340 in the first selector link 895, there is not adequate potential between ground and the multiple point to the lookout relays in the second and third selector links to permit operation of the lockout relays in these links. Accordingly, the second and third selector links cannot be utilized While the key I KI of the first selector link 895 occupies its select position.

Also, upon operating, the lookout relay R8 50 prepares, at the contacts 842, a point in a circuit, traced hereinafter, for energizing the upper winding of the test relay R850, prepares at the contacts 833, a point in a circuit, traced hereinafter, for energizing the lower winding of the test relay R850, prepares, at the contacts 8-14, a point in a circuit, traced hereinafter, for energizing the winding of the magnet M880 of the rotary switch S8530, interrupts, at the contacts 845, a point in a circuit, traced hereinafter, for energizing the winding of the magnet M385 oh the rotary switch S829, and interrupts, at the contacts 8-l6, a point in a circuit, traced hereinafter, for energizing the winding of the stop relay Ra'itil and for illuminating the pilot lamp arranged in the first group of pilot lamps on the indicator panel 200 and corresponding to the selected runway end on the flying field.

The dispatcher then operates the dial 30! in.

accordance with the number of the determined runway end on the flying field by inserting his finger in the appropriate hold in the finger disk 302 and then rotating the disk until his finger engages the finger stop 303. The finger disk 302 then returns to its normal position, thereby to cause the dial 30! to transmit a corresponding number of impulses. When the dial 30! is operated away from its normal position the contacts 1! and 1 1 thereof are actuated into engagement in order respectively to complete a path, traced hereinafter, for short-circuiting the winding of the test relay R130 and to complete a circuit for energizing the winding of the hold relay R150. The circuit for energizing the winding of the hold relay R150 extends from ground by way of the wiper 135 and engaged normal contact in the associated contact bank 136 of the rotary switch S180, C148, the contacts 163, C138, the contacts 1!1 of the dial 30!, the contacts 120 of the key IKI, C139, the contacts 144, and the winding of R150 to battery. When energized over the abovetraced circuit, the hold relay R150 operates to prepare, at the contacts 15!, a point in a circuit, traced hereinafter, for energizing the winding of the magnet M135 of the rotary switch S180, to complete, at the contacts 152, an obvious path for applying battery potential by way of the resistor 119 to the conductor C133, to complete. at the contacts 153, an obvious alternative holding circuit for energizing the winding thereof, and to interrupt, at the contacts 154 a point in a circuit, traced hereinafter, for energizing the lower winding of the switching relay R160.

After the finger disk 302 of the dial 30! is released, the dial operates to'transmit the corresponding number of impulses, as previously noted. More particularly, the contacts 1!5 of the dial 30! are operated into engagement and,

disengagement a number of times corresponding to the number of impulses to be transmitted. Each time the contacts 1!5 of the dial 30! are actuated into engagement, the previously mentioned circuit for energizing the winding of the magnet M135 of the rotary switch S180 is completed, assuming that the keys 2K! and 3K! individually associated with the second and third selector links occupy their normal positions. The last-mentioned circuit extends from ground by way of the contacts 181 of the key 3Kl, C159, the contacts 108 of the key 2Kl, C158, the contacts 12! of the key !K|, C134, the contacts 1!5 of the dial 30!, C132, the contacts 15! and the winding of M135 to battery. Each time the above-traced circuit is completed, the magnet M135 operates to condition the wipers noted of the rotary switch S180 to be driven one step in the clockwise direction; and each time this circuit is interrupted, the magnet M135 restores, thereby to cause the wipers noted of the rotary switch S180 to be driven one step in the clockwise direction. Also, each time the magnet M135 operates, it completes, at the contacts 136, an obvious circuit for energizing the winding of the slave relay R190, thereby to cause this relay to operate. Accordingly, the circuit for energizing the winding of the slave relay R190 is intermittently completed as the magnet M135 operates intermittently; however, the slave relay R190 does not restore during the intermittent restoration of the' magnet M135, as this relay is of the slow-torelease type. In fact, the slave relay R190 does not restore until a short time interval following the final restoration of the magnet M135. Upon operating, the slave relay R completes, at the contacts 19!, the previously mentioned path for short-circuiting the winding of the test relay R130, this path extending from ground by way of the contacts 19!, the winding of R130, the contacts 142, C133 and the contacts 1!6 of the dial 30! to ground. Also, when the wipers noted of the rotary switch S180 are operated away from their normal positions one step in the clockwise direction, the set of switch springs S1I8 is actuated into engagement, thereby to prepare an alternative circuit, traced hereinafter, for energizing the winding of the magnet M135, this circuit being retained interrupted at the contacts 122 of the key !K! at this time.

At the conclusion of the first digit the finger disk 302 of the dial 30! occupies its normal position and the contacts H5, H6 and N1 of the dial'30! are operated into disengagement: Also, at this time, the wipers noted of the rotary switch S180 are operated away from their normal positions a predetermined number of steps corresponding to the digit transmitted by the dial 30!. When the contacts 1l1 of the dial 30! are actuated into disengagement, the previously traced circuit for energizing the winding of the hold relay R150 is interrupted thereat; however, the hold relay R150 does not immediately restore, this relay being of the slow-to-release type. Also, when the contacts 1!6 of the dial 30! are actuated into disengagement the previously traced path for short-circuiting the winding of the test relay R is interrupted thereat. When the contacts 1!5 of the dial 30! are actuated into disengagement the previously traced circuit for energizing the winding of the magnet M is interrupted. The subsequent operation of the test relay R130 depends upon several conditions, including the particular digit dialed as will appear hereinafter. 7

Assuming that the digit dialed at the dial 30! is the digit 1, in this event the wipers noted of the rotary switch S180 are moved into engagement with the first contacts in the associated contact banks after the magnet M135 is deenergized. However, prior to the restoration of the slave relay R190 and subsequent to the re turn of the finger disk 302 of the dial 30! to its normal position, a circuit is' completed for energizing the winding of the test relay R130 in the event the corresponding runway end R! on the flying field has not been previously selected by either the second or the third selector links. This circuit extends from ground by way of the contacts 19!, the winding of R130, the contacts 142, C133, the contacts 152 and the resistor 119 to battery. When energized over the above-tracedcircuit, the test relay R130 operates to complete, at the contacts 13!, a circuit for energizing the lower winding of the start relay R140. This circuit extends from ground by way of the contacts 161 of the key SKI, C159, the contacts 168 of the key ZKI, C158, the contacts 12! of the key !K!, the contacts 13! and the lower winding of R to battery. When energized over the above-traced circuit, the start relay R140 operates to complete, at the contacts 146, an obvious holding circuit for energizing the lower Winding thereof. Also, upon operating, the start relay R140 interrupts, at the contacts 144, a further point in the previously traced holding circuit for energizing the winding of the hold relay R and prepares, at

141, an obvious path for applying ground poten- 1 tial-torthe conductor Cl'lrS' for a purpose more fully described hereinafter.

Shortly after the magnet M1555 restores, the slave relay R199 restores to interrupt, at the contacts 191, a further point in the previously traced circuit for energizing "the winding of the test relay R131, Shortly after the: previously traced holding circuit for energizing the wind ing of the hold relay R156 is interrupted; this relay restores to interrupt, at the contacts i, a further point in the previously; traced: circuit for energizing the Winding. of the magnet M735, tointerrupt, at the contacts 152; a point in the previously tracedi original circuit for applying battery potential by way of the resistor- Hi? to the conductor C183, to interrupt, at the contacts153, the previously mentioned path for applying ground potential to the conductor C138, and to complete, at the contacts T5 3, -a'cir'cuit, traced hereinafter, for energizing the lower winding ofthe switching relay R1653.

At this time the wipers noted of, the rotary switch S1 80 engage the first contacts in t 13 associated contact banks as previously explained.

Specifically, the wiper T85 of the rotary switch S180 engages the first contact in the associated contact bank 185, thereby tocompl'etethe 'pre viously mentioned circuitfor energizing. the lower winding of the switching relayRlt'il; this circuit extending from ground" by way 'of' the wiper 185 and engaged first contact inthe associated contact bank 1%; CH9, the contacts 154 and the lower winding of R759 to battery. When energized over the above-traced'circuit, the switching relay R160 operates to complete, at the contacts I56, a holding circuit for energizing the upper winding thereof; this circuit extending from ground by Wayof the contacts 161 of the key 3K1, C159, the contacts T? of thekey-xZ-KI, C158,, the contacts l2lof the: key IKI, C151, the contacts 756 and the upper wind ing of R150- to battery. Also, upon operating; the switching relay'Rliiu'interrupts, at the contacts 1-H, an obvious connection between the wiper 1-8I* of the rotary switch S186 and the con ductor-G'I33, completes, at the contacts 152, an obvious connection between the wiper T83- of the rotary switch S138- and the conductor C733; interrupts, at the contacts 163; a further point in the previously traced original path for applying ground potential by way of'the Wiper-E85 and engaged normal contact in the associated contact bank 185 to the conductor C138, and completes, at the contacts 154, an obvious alternative path forapplying ground potential by way of the wiper 18-5 and engaged first contact in the associated contact bank 186- to the conductor C738. Finally, the switching relay Rite prepares, at the contacts I65, a point in acircuit, traced hereinafter, for energizing the upper winding of the start relay R149. At this time battery potential is applied by way of the resistor 119', the contacts 152, the contacts T52, the Wiper I83 and engaged first contact in the associated contact bank'184, C141 and the firstcohductor in the: cable. 1T8v to the first contact in the contact bank 802-- of the rotary switch S8211} in the first selector link 885; Also, the application of ground potential to the conductor CW8 completes a circuit for initiating the operation of the first selector link 895 in a manner more fully described hereinafter.

Inv the foregoing description it was assumed that the runway end RI had not been previously selected by either the second or third selector links when the corresponding digit 1 was dialed. Assumingnow that when the digit 1 is dialed, the corresponding runway'end RI has been previously selected by either the second or third selector links, the previously traced circuit for energizing the winding of the test relay R133 is not completed when the dial 391 is returned to its normal position. More particularly, in this event, when the dial SM is returned to its normal position to interrupt, at the contacts H6 thereof, the previously traced path for shortcircuiting the winding of the test relay R139, an alternative path for short-circuiting the winding of the test relay RES!) is completed. This alternative path for short-circuiting the winding of the test relay R139 extends from ground by way of the contacts 19!, the winding of R132}, the contacts l -i2, 6133, the contacts 151, the wiper 1-85 and engaged first contact in the associated contact bank ofthe rotary switch $789 to the corresponding first conductor in the cable T16; the last-mentioned conductor in the cable 776 having ground potential appearing thereon in a manner more fully described hereinafter; Accordingly, at this time, the test relay R138 does not operate. Hence, after the slave relay R790 and the hold relay R15il-restore,:only the switching relay R768 occupies its operated position. In view of the fact that the start rel'ay R140 is not operated to complete, at the contacts Ml, the previously mentioned path for applying ground potential to the conductor C178,. operation of the first'selectorlink 895" is not initiated at this time.

In the foregoing description it was assumed that the first digit dialedat the dial 39] was the digit]. Assuming now that the first digit dialed is some other digit other than 1 and any digit between 2 and'o, such, for example, as the digit 4', at the conclusion of the digit the finger disk 332 of the dial 3M is returned to its normal position, thereby to interrupt, at the contacts N6, the previously traced path for short-circuiting the winding of the test relay EH33; At this time the wipers noted of the rotary switch SE engage the'fourth contacts in the associated contact banks and the previously traced circuit is completed for energizing the winding of the test relay R in the event the corresponding runway end R4 on the flying field has not been previously selected by either the second or the third selector links. When thus energized. the test relay R'ESU operates, as previously explains-d, thereby to' cause the start relay R350 to operate, whereupon operation of the first selector link 8S5 is initiated, as previously explained;

On the other hand, in the event the runway end R4 has been previously selected by either the second or third selector links, an alternative path for shortcircuiting the winding of the test relay PJSO' is completed when the dial 535! is returned to its'normal' position. Accordingly, op eration ofthe first selector link 895 is not init iated in this event, as previously explained.

In the foregoing descriptions it was assumed that only one digit was dialed at the dial 301 Assuming now that two digits are to be dialed at the dial 301, the first digit comprising the digit 1 and the second digit comprising any digit between the digits 1 and 8, such, for example, as the digit 2, a first digit 1 and a second digit 2 being dialed when it is desired to select the runway end R12 on the flying field, At the conclusion of the first digit 1 the apparatus in the impulse receiver unit 100 occupies one of two conditions, depending upon whether the corresponding runway R1 on the flying field has been previously selected by either the second or third selector links, as previously explained.

Assuming that the runway end R1 on the fiying field has not been previously selected by either the second or third selector links'when the first digit 1 is dialed, the apparatus in the impulse receiver unit 100 occupies the condition initially explained and the finger disk 302 of the dial 301 is again actuated in accordance with the digit 2. In this event, when the finger disk 302 of the dial 301 is actuated away from its normal position, the contacts 111 in the dial 301 are actuated into engagement, thereby to complete the previously mentioned circuit for energizing the upper winding of the start relay R140, this circuit extending from ground by way of the wiper 185 and engaged first contact in the associated contact bank 188, C149, the contacts 3164, C138, the contacts 111 of the dial 301, C156, the contacts 120 of the key 1K1, C139, the contacts 145 and 165 and the upper winding of R140 to battery. When the upper winding of the start relay R140 is energized over the abovetraced circuit, the lower winding thereof being energized by Way of the previously tracedlhoiding circuit, the start relay R140 restores, this relay being of the differential type. Uponrestoring, the start relay R140 interrupts,'at the contacts 145, the previously traced circuit for energizing the upper winding thereof and interrupts, at the contacts 146, the previously traced holding circuit for energizing the lower winding thereof. Further, the start relay R140 completes, at the contacts 144, the previously traced circuit for energizing the winding of the hold relay R150, thereby to cause the latter relay to operate. Also, the start relay R140 interrupts, at the contacts 143. the previously traced alternative circuit for applying battery potential by way of the resistor 119 to the conductor C133, prepares, at the contacts 142, the previously traced path for short-circuiting the winding of the test relay R130. and interrupts, at the contacts 141, the previously mentioned path for applying ground potential to the conductor C118. ing, the hold relay R150 completes, at the contacts 151, the previously mentioned circuit for energizing intermittently the winding of the magnet M135 of the rotary switch S180 by way of the dial 301.

When the finger disk 302 of the dial 301 is re leased, the dial 301 operates to transmit a second series of impulses corresponding to the second digit, thereby to cause the magnet M135 to operate intermittently and drive the wipers noted of the rotary switch S180 a corresponding number of additional steps in the clockwise direction. At the conclusion of the second digit the wipers noted of the rotary switch S180 engage contacts in the associated contact banks disposed one step in advance of the number of impulses v included in the second digit. At the conclusion .circuit is completed for sh'ort-circuiting the Upon operatof the digit the finger disk 302 of the dial 301 is returned to its normal position, thereby to interrupt, at the contacts 116, the previously traced 'path for. short-circuiting the winding of the test relay R130. At thisitime thewipers noted of the rotary switch S180 engage the third contacts in. the associated. contact banks and thepreviously traced circuit is completed for energizingithe winding l of the test relay R130 in theevent the corresponding runway end R12 on the fiyingffield has not,.been previouslyselected by either the second or thirdselector links.

.I. lOn the other hand, in the event the runway end R12 has been previously selected by either the. second. or third selector links, analternative winding of the test relayR130, this circuit. ex-

:tendingj'from ground'by way of the contacts 191,

the winding of R130, thecontacts 142, C133, the

contacts 162, the wiper 183 and engaged third contactl'in theiassociatedicontact bank. 184 of 'the rotary switch S180 tothe corersponding conductor in the. cable 111;, this conductor having ground potential. appearing thereon, in. a mannerifnore; fully described hereinafter; Accordingly, 'in'th'is event; operation .of the first selector link 895jsnot initiated, 5 1

Assuming that. thevrunway end R1 onthe flying field has been previously selected; when the digit jlfis dialed the-:apparatus in'the impulse receiver1unit .100 occupies thefcondition explained 'aboveand,the;'finger-diska302, of the dial 301 is again ga'ctuatefd in accordance with the' digit 2. Inrthiseve'nt,iwhenithe -finger .disk 302 offthe dial*3.0:1 iszactuated away from its normal position,.the .contacts'll'l ofqthe dial 301 are actuatediintojengagement, thereby to complete di- .re.ct1y.;anralternative circuit'for energizing the winding: of. thehold relay R150. This alternative circuit for 'energizingpthe winding of the hold .relay-R150extendstrom' ground. by way of the wip.er*1,85 andengaged first contact in the assotional digit transmitted by the dial 301. The

subsequent operation of the impulse receiver unit is the same as that previously explained, the operation of the test relay R at theconclusion of. the second digit 2 being dependent upon whether the runway end R12 on the flying field has been previously selectedby either the second or the third selector links, as previously noted.

From the foregoing. description of theoperation of. the impulse receiver unit 100 it is noted that,x at the conclusion of any digit or digits dialed at the dial 301,'the previously traced circuit forenergizing thewinding of the test relay R130 is completed only in the, event the corre sponding runway end on the flying field has not been previously selected by either the second or third selector links. On the other hand, in the event the corresponding runway end on the flying field hasbeen previouslyselected by the second or third selector links, the previously traced circuit for energizing the winding of the test relay R130 atthe conclusion of thedigit is not completed'in view of the fact that an alternative circuit for short-'circuiting the, winding of the test relay R130 is completed. As previously noted, thisaltern'ative: circuit. extends from ground by..way.of'the contacts Till, the. winding of.:R130. and the contacts .142 to the conductor S180, or from theconductor'C133 by way .of the contactsJfiZ to the wiper 183 of the rotary switch S180, the wiper 18L of the rotary switch S180 engaginga contactin the'associated-contact bank :182 having ground potential appearing thereon inthe event the digit dialed comprises any digit between 1 and. and the wiper .183 of therotaryswitch S180 engaging a contact in the associated contact bank 182 having ground potential appearingthereon'in the event the digit 1 V dialed comprises any digit between 11 and 18.

The ground potential appearing on the contact in the contact bank 182 engaged by the wiper 18I.of the rotary switch S180is derived by way ofthe 'correspondingconductor in the cable 118 from a contact bank in either the second 'or third selector links corresponding to the contact .bank

802 .of the rotary switch-S800 in the first selector link895, in the event the corresponding runway endon th flying fieldhas been previously se-;

end on theflying field has beenpreviously selected by the second or third selector links. Accordingly, the test relay R130 in the impulse receiver unit 100 is not operated in the event the determined runway end on the flying field has been previously selectedby either the second or third selector links. Hence, the start relayR140 in the impulse receiver unit 100 is not operated to initiate operation of the first selector link 895 in this event, 7

Further, it is noted that, in the eventthe determined runway end has not been previously selected by the second or third selector links, the operation of the start relay-R140 in the impulse receiver unit 180 is efiective not only tolinitiate operation of the first selector'link 895, but to mark with battery potential by way of the re sistor 119 and the previously traced circuit a particular contact in the contact banks 182 or 184 of the rotary switch S180 corresponding to the determined runway end on the flying field.

This marking of the contact in the contact banks 182 or 184 of the rotary switch S180 is effective to control the operation 'ofthe first selector link 895 in a manner more fully described hereinafter. Also, it is noted that the impulse receiver unit 100 is so connected and arranged that-it is responsive to a second digit after a first digit has been dialed only intheevent the first digit dialed is the digit 1.

switch S180 and corresponding .to the. twelfth contactin lthe cont-act...bank 802. hi the,.rotary .C133,f.fr'om; the conductoriC133 by way of the. contacts .16I tothe wiper 18I ofthe rotary switch lower winding of the test relay R850 extends bank 184 engaged by thewiper 183 .of the rotary switch- S1-80 is ma1=ked--with battery potential,

this marking path extending from battery by way-of-the resistor *1 19, thecontacts 143, C133, the -contacts: 162, the wiper 183 I and engaged third. contact in the 0 associated contact bank .184 of the-rotary switch S180 and the-corresponding conductor in the cable 111 tothe twelfth conthe winding .of the magnet M880 of the rotary switch-S800. The circuit for energizing the from the grounded-conductor C118 byway of the 'contacts843, the resistor 811 and the lower winding of R850 to battery; and the circuit'for energizing. the winding ofthe magnet M880 extends fmmpthe grounded conductor C118 by way. of thecontacts 844, 85?) and 88! and the winding -0fgM880 to battery. When the lower winding of the test'relay-R850- is thus energized,

this relay becomes extremely 'fastto operate .when the upper winding thereof -is energized.

When the windingof -themagnet-M880 is thus energized,this-magnetoperates to interrupt, at .the contacts 188I, the-previously traced circuit .for energizing the-.=winding thereof, thereby to cause the magnet M880 -to restore and recomlplete, at the contacts 88!, the previously-traced circuit .forenergizing the winding thereof. Ac-

. cordingly, the magnet -M880 operates intermittently, therebyi'toeause the wipers noted of the rotary .switchS880 to be. driven step-by step in .the.counterclockwise direction until the wiper 88! engages the twelfth contact in the associatedcontact bank802 marked with battery povtential aspreviously explained. When the wiper engages the twelfth contact in the associ- .ated :contactbank 8820f the rotary switch S800,

the previously, mentioned circuit for energizing .the. upper winding offthe test relay-R850 is completed, this circuit extending .from ground by way of, .thescontacts4842, theupper winding of R850, C864 and the wiper. 80l tothe twelfth contact in. the associated contact bank802, this contact having; battery.v potential appearing thereon. Whentheupper winding of the test relay R850 is thus energized, this relay operates exceedingly fast to interrupt, :at the contacts 855, the previously .tracedcircuit for energizing the winding of the magnet M880, thereby to arrest for applying direct ground potential to the conductor'C88'4, thereby to mark with ground potential by way of the wiper80l and engaged twelfth contact in the associated contact bank of the arotaryiswitch-swfl the corresponding conductor .iILIhGJCRbIE T IT.

This application of-marking ground potential to the twelfth conductor in the cable 111 marks the corresponding runway end RI 2 on the flying field against selection by either the second or third selector links. Also, upon operating, the test relay R850 interrupts, at the contacts 852, the previously mentioned path for short-circuiting the lower winding of the lockout relay R840, thereby to render the lockout relay R840 relatively fast to release when the key IKI is operated from. its select position back to its normal position. Also, upon operating, the test relay R850 prepares, at the contacts 85I, an alternative holding circuit, traced hereinafter, for energizing the lower winding thereof and completes, at the contacts 856, a circuit for energizing the winding of. the marking relay R890. The circuit for energizing the winding of the marking relay R890 extends from ground byway of the contacts 856, the wiper 803 and engaged twelfth contact in the associated contact bank 804 of the rotary switch S800, and the winding of R890 to battery. When energized over the above-traced circuit, the marking relay R890 operates to complete, at the contacts 89I, 892, etc., obvious paths for applying ground potential by way of the grounded conductor C893 to the fifteen conductors included in the cable 896, for a purpose more fully described hereinafter. Further, the test relay R850 prepares, at the contacts 850, a circuit, traced hereinafter, for energizing the winding of the stop relay R860 in multiple with the pilot lamp 2I2 in the first and prepares, at the contacts 858, a circuit,

traced hereinafter, for energizing the upper winding of the switch-through relay R810.

Also; the test relay R850 completes, atthe contacts 851, a path for applying ground potential to the fourth contact in the contact bank 808 of the rotary switch S800, this path extending from ground by way of the contacts 851, C866, the wiper 804 and engaged twelfth contactin the associated contact bank 806 and C818 to the fourth contact in the contact bank 808 of the rotary switch S800. It is noted that ground potential is applied to the fourth contact in the contact bank 808 of the rotary switch S800 in view of the fact that the runway end R4 on the flying field is opposed to thedetermined runway end-RI2 thereon. As previously noted, upon operating, the marking relay R890 applies ground potential to the fifteen conductors included in the cable 896, which conductors are terminated by the contacts I to 3, inclusive, 5 to II, inclusive, and I4 to- I8, inclusive, in the contact bank 808 of the rotary switch S800, the runway end R3 being an opposing runway end to the determined runway end RI2 on the flying field and the runway ends RI, R2, R5 to RI I, inclusive, and RI4 to RI8, inclusive, being intersecting runway ends with respect to the determined runway end RI2. Accordingly, at this time, all of the contacts, with the exception of the twelfth and thirteenth contacts in the contact bank 808 of the rotary switch S800 are marked with ground potential due to the fact that the runway end RI2 is the determined runway end and the runway end RI3 is the only other runway end not conflicting with the determined runway end RI2. Further, it is noted that the marked contact in the contact banks 802 and 808 of the rotary switch S800 in the first selector link 805 are multipleol to corresponding contacts in the con- .tact banks of corresponding rotary switches in the second and third selector links, thereby 'to prevent the second and third selector links from seizing trunks associated with conflicting runway ends on the flying field, as will be explained more fully hereinafter.

Finally, upon operating, the test relay R850 prepares, atthe contacts 859, a circuit for energizing the winding of the magnet M885 of the rotary switch S820, which circuit is completed when the dispatcher in the dispatcher control tower IOI returns the key IKI of the first selector link 895 from its select position to its normal position. Before the dispatcher in the dispatcher control tower IOI returns the key IKI from its :select position to its normal position, he first operates the keys IK2 and IK3, the key IK2 being operated in accordance with the use to be made of the determined runway end RI2 and the key I K3 being operated in accordance with thevisual condition of the flying field. In the event the. flying field is clearly visible and illumination of the contact lamps disposed along the margins of the runway R4-RI2 is not required, the key IK3 is operated to its trafiic-on position. On the other hand, in the event the flying field is not clearly visible and illumination of the contact lamps disposed along the margins of the runway R4RI2 is required, the key IK3 is operated to its runway and trafiic-on position.

Assuming that the flying field is clearly visible and thatthe determined runway RI 2 i to be used by an airplane taking off, the key IK3 is operated to its traflic on position and the key IK2 is retained in its take off position. After the keys- IK2 and IK3 have been thus operated, the key IKI is returned from its select position to its normal position. When the key IKI is returned to its normal position, the previously traced holding circuit for energizing the upper windingof the lockout relay R840 is interrupted, at-the contacts 124 of the key IKI, thereby to cause the'lockout relay R840 to restore. Also, when the key IKI is returned to its normal position, the previously mentioned alternative holding circuit for energizing the lower winding of the testrelay R850 is completed, this circuit extending from ground by way of the contacts 123 of the key IKI, C169, the contacts 125 of the key IKI, C194, the contacts 85I and the lower winding of R850 to battery. Also, when the key IKI is returned to its normal position, the previously traced holding circuits for energizing in multiple the lower winding of the start relay R and the upper winding of the switching relay R are interrupted, thereby to cause these relays to restore. Further, when the key IKI is returned to its normal position, the previously mentioned alternative circuit for energizing the windin of the magnet M135 is completed, this circuit-extending from ground by way of the contacts 161 of the key 3KI, C159, the contacts 168 of the key 2KI, C158, the contacts 122 of the key IKI, the set of switch springs S1I8, the contacts 131 and the winding of M135 to battery. When energized over the above-traced circuit, the magnet M135 operates to interrupt, at the contacts 131,

the previously traced alternative circuit for ener.

gizing the winding thereof, thereby to cause the magnet M135 to restore and recomplete, at the contacts 131, the previously traced circuit for energizing the winding thereof. Accordingly, the magnet M135 operates intermittently in order to drive the wipers noted of the rotary switch S in the clockwise direction back into their normal positions, whereupon the. set of switch springs 

